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Virginia Cooperative Extension - Knowledge for the CommonWealth

Dry Cows Need Heat Stress Relief Too

Dairy Pipeline: June 2006

Sue Puffenbarger
Dairy Science Extension Agent, Franklin County
(540) 483-5161 email:

This is the time of year to get serious about heat abatement strategies for your herd. Though we enjoy the warmer weather, most lactating cows perform best at temperatures from 40 - 65°F. Signs of heat stress start to occur at around 75°F. This spring, once you've installed your new fans and sprinkler systems and cleaned off your existing fans in the lactating herd, you also need to consider making sure that your close up dry cows are kept cool.

Research has shown that cows experiencing even mild heat stress in late gestation, suffer various problems at calving and in the subsequent lactation. Various research trials have shown that there are significant effects of heat stress that directly affect a cow's next lactation and the health of the calf. These include: shorter gestation length, decreased calf birth weights, increased incidence of retained placentas and the subsequent health problems associated with RP's, decreased dry matter intake (and we all now how critical that is to the next lactation), decreased colostrum quality, decreased calf vigor, decreased absorption of immuno-globulin by the calf, decreased milk production and a reduction in fertility postpartum. All this and they haven't even started milking yet!

Remedies for heat stress are similar to those for cooling lactating cows, though significantly cheaper due to fewer cows requiring investment. For those that don't have a facility, shade is extremely important. You can purchase a shade cloth to make an artificial shade shelter very inexpensively. This option is better than using existing trees for numerous reasons including mastitis prevention and extending the life of your trees! Availability of clean water is also very important. Cows need access to 3 - 4 linear inches of trough space per cow. If you have facilities, fans and sprinkler systems are very effective at keeping body temperatures down. A sprinkler system at the feed bunk will help to maintain dry matter intake at this critical time period.

So, should you be thinking about cooling your dry cows this summer? Yes. Research has shown time and time again that by doing so, you can improve milk production, overall health of the cow and calf and improve reproduction. Remember, that maximizing comfort, reducing stress and providing a properly balanced ration for your dry cows will ensure that she is set up for the lactation to come. For more information on cow cooling, see Dairy Pipeline article "It's summer time! Are your cows cool?" - July 2004.

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